The City was in shock last night after the apparent suicide of a millionaire financier haunted by the pressures of dealing with the credit crunch.

Kirk Stephenson, who was married with an eight-year-old son, died in the path of a 100mph express train at Taplow railway station, Berkshire.

Mr Stephenson is believed to have taken his own life after succumbing to mounting personal pressures as the world’s financial markets went into meltdown.

The death of the respected 47-year-old City figure evokes memories of the 1929 Wall Street crash in America and comes as:

• Bradford & Bingley teeters on the brink of nationalisation after a dramatic share price slump.

• David Cameron faced embarrassment on the eve of the Tory conference after members of a secretive club of Conservative donors were linked to the ‘short-selling’ of Bradford & Bingley.

• Gordon Brown was wrongfooted by Shadow Chancellor George Osborne, who announced plans to set up an independent watchdog to police the Treasury and strip it of key powers if the Conservatives win the next Election.

New Zealand-born Mr Stephenson, who owned a Ј3.6million, five-storey house in Chelsea and a retreat in the West Country, was chief operating officer of Olivant Advisers.

Last year, the private equity firm tried to buy a 15 per cent stake worth almost Ј1billion in Northern Rock before the bank was nationalised, bidding against Virgin boss Sir Richard Branson.

In June, the company secured a 2.5 per cent stake in Swiss banking giant UBS. There has been persistent speculation in the financial world that UBS has written off billions after being exposed to the US mortgage market.

Since June, the bank has dropped in value by about 20 per cent, which means the value of Olivant’s stake in UBS has fallen from Ј950million to Ј770million.

Before his death at 9am on Thursday, Mr Stephenson appeared to have everything to live for.

A glittering 20-year City career had made him a hugely wealthy man and he was said to have been happy in his marriage to Karina Robinson, a successful financial writer.

Sources stressed that neither Mr Stephenson nor his company had financial problems that would have led him to take his own life.

But they said the financier had ‘succumbed’ to the stress and responsibilities of his taxing role, adding that Mr Stephenson had overreacted to the continuing financial turmoil.

After eating breakfast on Thursday with his wife and their young son Lucas, Mr Stephenson drove to Taplow station, left his car in the car park and crossed a footbridge over the main First Great Western Plymouth to Paddington line.

Out of view of passengers on the platform, he is then said by witnesses to have leapt in front of a high-speed train.

The driver sounded his horn and slammed on the brakes but was unable to stop in time. The train came to a standstill a mile down the track.

Mr Stephenson left no note, but the incident is being treated by police, train operator First Great Western and his own firm as a suicide.

In due course a coroner will examine the death and record an official verdict.

Mr Stephenson’s colleagues and family were unable to explain why had he had gone to Taplow.

Last night, his devastated widow released a statement saying: ‘Kirk was a life-enhancer – not with a showy, life-and-soul-of-the-party sort of charisma, but as a planner who quietly ensured everyone around him had a marvellous time.

‘A dedicated father and a devoted husband, he valued his family above all else.

'He had a gift for friendship and was a generous and exceptional host, gathering his wide circle in summer villas all over Europe, as well as for parties, dinners and opera.

‘Any occasion with Kirk was a wonderful experience. He spent many a fine – and less than fine – summer evening listening to opera at Garsington, Glyndebourne and The Grange with friends.

'He also loved board games and tennis, passions he shared with his treasured son, Lucas.

‘He arrived in London in 1983 as an SG Warburg trainee. After his stint in the City he went on to work at several large organisations. Latterly, he was a director for Olivant.

‘Always a keen traveller, in 1999 he married his cherished wife Karina. Together they travelled from Bhutan to Burgundy, Buenos Aires to Tripoli.

‘He will be sorely missed by his wife, his son, his mother Bet Stephenson, and his many friends.’

Until two months ago, former merchant banker Karina was a columnist on The Banker magazine.

One of her former colleagues said: ‘It is shocking news. I know Kirk had been under pressure, but I am not aware that his own money was at stake.

'He was very hard-working. He did a 24-hour-a-day job.’

A family friend added: ‘Kirk was always troubled because of his work. He was always so busy, working late and travelling a lot.

'But he didn’t seem any different on Thursday. He ate breakfast with the family, kissed them and said goodbye. No one can believe what happened.’

Mr Stephenson’s previous jobs include chief operating officer of City lawyers Freshfield Bruckhaus Deringer, group finance director of Coats Viyella and Amersham International and an investment banker at Warburg and Morgan Stanley.

At Olivant Advisers he was paid Ј333,000 last year, but is thought to have made millions more from the core Olivant business, based in Guernsey.